Power Converter Package Including Vertically Stacked Driver IC

ABSTRACT

In one implementation, a semiconductor package includes a control conductive carrier having a die side and an opposite input/output (I/O) side connecting the semiconductor package to a mounting surface. The semiconductor package also includes a control FET of a power converter switching stage attached to the die side of the control conductive carrier, and a driver integrated circuit (IC) for driving the control FET. The driver IC is situated above the control FET and is electrically coupled to the control FET by at least one conductive buildup layer formed over the control conductive carrier.

The present application claims the benefit of and priority to aprovisional application entitled “Power Converter Package IncludingVertically Stacked Driver IC,” Ser. No. 61/715,749 filed on Oct. 18,2012. The disclosure in this provisional application is herebyincorporated fully by reference into the present application.

BACKGROUND Background Art

Power converters are used in a variety of electronic circuits andsystems. Many integrated circuit (IC) applications, for instance,require conversion of a direct current (DC) input to a lower, or higher,DC output. For example, a synchronous buck converter may be implementedas a voltage regulator to convert a higher voltage DC input to a lowervoltage DC output for use in low voltage applications in whichrelatively large output currents are required.

The voltage converted output of a synchronous buck converter istypically provided by a power switching stage including a high sidecontrol switch and a low side synchronous (sync) switch, which may bedriven by a driver IC of the buck converter. Drive signals from thedriver IC may be routed to the power switching stage through a printedcircuit board (PCB) or package substrate. Consequently, packagingsolutions for such power converters must typically be sized toaccommodate a side-by-side layout including not only the control andsync switches of the power converter switching stage, but the driver ICfor those power switches as well.

SUMMARY

The present disclosure is directed to a power converter packageincluding a vertically stacked driver integrated circuit (IC),substantially as shown in and/or described in connection with at leastone of the figures, and as set forth more completely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of an exemplary power converter circuit.

FIG. 2 shows a cross-sectional view of an exemplary semiconductorpackage suitable for use as a power converter package and including avertically stacked driver integrated circuit (IC).

FIG. 3 shows a flowchart presenting one exemplary method for fabricatinga semiconductor package suitable for use as a power converter packageand including a vertically stacked driver IC.

FIG. 4A shows an exemplary structure corresponding to an initial stageof the method described in FIG. 3.

FIG. 4B shows the exemplary structure in FIG. 4A at an intermediatestage of the method described in FIG. 3.

FIG. 4C shows the exemplary structure in FIG. 4B at another intermediatestage of the method described in FIG. 3.

FIG. 4D shows the exemplary structure in FIG. 4C at another intermediatestage of the method described in FIG. 3.

FIG. 4E shows the exemplary structure in FIG. 4D at another intermediatestage of the method described in FIG. 3.

FIG. 4F shows the exemplary structure in FIG. 4E at another intermediatestage of the method described in FIG. 3.

FIG. 4G shows the exemplary structure in FIG. 4F at another intermediatestage of the method described in FIG. 3.

FIG. 4H shows the exemplary structure in FIG. 4G at another intermediatestage of the method described in FIG. 3.

FIG. 5 shows a cross-sectional view of an exemplary semiconductorpackage suitable for use as a power converter package and including avertically stacked driver IC, according to another implementation.

DETAILED DESCRIPTION

The following description contains specific information pertaining toimplementations in the present disclosure. One skilled in the art willrecognize that the present disclosure may be implemented in a mannerdifferent from that specifically discussed herein. The drawings in thepresent application and their accompanying detailed description aredirected to merely exemplary implementations. Unless noted otherwise,like or corresponding elements among the figures may be indicated bylike or corresponding reference numerals. Moreover, the drawings andillustrations in the present application are generally not to scale, andare not intended to correspond to actual relative dimensions.

As stated above, power converters such as voltage regulators are used ina variety of electronic circuits and systems. For instance, and as notedabove, integrated circuit (IC) applications may require conversion of adirect current (DC) input to a lower, or higher, DC output. As aspecific example, a buck converter may be implemented as a voltageregulator to convert a higher voltage DC input to a lower voltage DCoutput for use in low voltage applications in which relatively largeoutput currents are required.

FIG. 1 shows a diagram of an exemplary power converter circuit. Powerconverter 100 includes power converter multi-chip module (MCM) 102,output inductor 104, and output capacitor 106. As shown in FIG. 1, MCM102 includes switching stage 101 of power converter 100, and driver IC194 implemented to provide drive signals to switching stage 101. Asshown in FIG. 1, power converter 100 is configured to receive an inputvoltage V_(IN), and to provide a converted voltage, e.g., a rectifiedand/or stepped down voltage, as V_(OUT) at output 105.

Switching stage 101 may be implemented using two power switches in theform of metal-oxide-semiconductor field-effect transistors (MOSFETs)configured as a half bridge, for example. That is to say, switchingstage 101 may include high side or control switch 120 (Q₁) having drain122, source 124, and gate 126, as well as low side or synchronous (sync)switch 130 (Q₂) having drain 132, source 134, and gate 136. Controlswitch 120 is coupled with sync switch 130 at switch node 129, which, inturn, is coupled to output 105 through output inductor 104. Respectivecontrol and sync switches 120 and 130 may be implemented as group IVbased power devices, such as silicon power MOSFETs having a verticaldesign, for example. Power converter 100 may be advantageously utilizedas a voltage converter, for example a buck converter, in a variety ofautomotive, industrial, appliance, and lighting applications.

It is noted that in the interests of ease and conciseness ofdescription, the present inventive principles will in some instances bedescribed by reference to specific implementations of a buck converterincluding one or more silicon based power FETs. However, it isemphasized that such implementations are merely exemplary, and theinventive principles disclosed herein are broadly applicable to a widerange of applications, including buck and boost converters, implementedusing other group IV material based, or group III-V semiconductor based,power transistors. It is noted that as used herein, the phrase “groupIII-V” refers to a compound semiconductor including at least one groupIII element and at least one group V element. By way of example, a groupIII-V semiconductor may take the form of a III-Nitride semiconductorthat includes nitrogen and at least one group III element. For instance,a III-Nitride power transistor may be fabricated using gallium nitride(GaN), in which the group III element or elements include some or asubstantial amount of gallium, but may also include other group IIIelements in addition to gallium.

The connection between control switch 120 and sync switch 130 providingswitch node 129 can be implemented using a conductive clip, such as acopper clip, which must be sufficiently robust to accommodate highcurrent. Moreover, because control switch 120 and sync switch 130 can behighly sensitive to electrical resistance, the cross-sectional area ofthe conductive clip used to provide switch node 129 is often relativelylarge. In addition, control and sync switches 120 and 130 are capable ofgenerating substantial heat during operation. As a result, packagingsolutions providing thermal protection to control and sync switches 120and 130 may include a heat spreader, which is often also relativelylarge. Consequently, a packaging solutions for MCM 102 must typically besized to accommodate not only driver IC 194 and control and syncswitches 120 and 130, but a large heat spreader providing thermalprotection for the power switches and a large conductive clip for theirconnection as well.

The present application discloses a packaging solution enabling omissionof the aforementioned heat spreader and switch node conductive clip,while concurrently providing a highly compact design for packagingdriver IC 194 and switching stage 101 together. In one implementation, acontrol conductive carrier and a sync conductive carrier utilized,respectively, as structural supports for control switch 120 and syncswitch 130, are configured to provide integrated heat spreading. Inaddition, the support structure used to provide the control conductivecarrier and the sync conductive carrier can also be used to provideswitch node 129, as well as to electrically couple driver IC 194 to oneor both of control switch 120 and sync switch 130. FIG. 2 shows anexemplary representation of such a packaging solution.

FIG. 2 shows a cross-sectional view of semiconductor package 202attached to mounting surface 290, which may be a printed circuit board(PCB) for example, by solder bodies 292. Semiconductor package 202includes control conductive carrier 210 c having die side 208 c andopposite input/output (I/O) side 218 c connecting semiconductor package202 to mounting surface 290. Semiconductor package 202 also includessync conductive carrier 210 b having die side 208 b and opposite I/Oside 218 b also connecting semiconductor package 202 to mounting surface290.

Semiconductor package 202 further includes control FET 220 (Q₁) havingdrain 222, source 224, and gate 226, as well as sync FET 230 (Q₂) havingdrain 232, source 234, and gate 236. As shown in FIG. 2, control FET 220is attached to die side 208 c of control conductive carrier 210 c, andsync FET 230 is attached to die side 208 b of sync conductive carrier210 b. Semiconductor package 202 also includes conductive carriersection 210 a, and conductive buildup layers 221 a, 221 b, 221 c, and221 d (hereinafter “conductive buildup layers 221 a-221 d”). Inaddition, semiconductor package 202 includes electrically conductive dieattach material 219, first patterned dielectric 240, insulator 270filling isolation trenches 260 a, 260 b, and 260 c (hereinafter“isolation trenches 260 a-260 c”), and second patterned dielectric 250providing surface 252.

Also included as part of semiconductor package 202 are control draincontact 223 provided by control conductive carrier 210 c, sync sourcecontact 235 provided by conductive carrier section 210 a, respectivecontrol and sync gate contacts 227 and 237 including respectiveconductive buildup layers 221 d and 221 b, and switch node contact 229provided by sync conductive carrier 210 b. It is noted that, in additionto providing sync source contact 235, switch node contact 229, andcontrol drain contact 223, respective conductive carrier section 210 a,sync conductive carrier 210 b, and control conductive carrier 210 cprovide integrated heat spreading functionality for sinking heatgenerated in semiconductor package 202 away from control and sync FETs220 and 230 and into mounting surface 290.

As shown in FIG. 2, another advantage of providing integrated heatspreading using conductive carrier section 210 a, sync conductivecarrier 210 b, and control conductive carrier 210 c is the verticalspace available for driver IC 294 due to omission of a separate heatspreader for control and sync FETs 220 and 230. For example, and asfurther shown in FIG. 2, in one implementation, driver IC 294 may besituated above one or both of control and sync FETs 220 and 230. Asshown in FIG. 2, driver IC 294 may be attached to at surface 252 ofsemiconductor package 202 using die attach material 293. Also shown inFIG. 2 is encapsulation material 298 covering driver IC 294.

Driver IC 294 can be electrically coupled to one or both of respectivecontrol and sync gate contacts 227 and 237 of respective control andsync FETs 220 and 230. Thus, driver IC 294 may be electrically coupledto gate 226 of control FET 220 by control gate contact 227 throughconductive buildup layer or layers 221 d formed over control conductivecarrier 210 c. In addition, or in the alternative, driver IC 294 may beelectrically coupled to gate 236 of sync FET 230 by sync gate contact237 through conductive buildup layer or layers 221 b formed over syncconductive carrier 210 b. Moreover, as shown in FIG. 2, in oneimplementation, driver IC 294 can be electrically coupled to one or bothof control and sync gate contacts 227 and 237 including respectiveconductive buildup layers 210 d and 210 b by bondwires 296.

Semiconductor package 202 corresponds in general to MCM 102 in FIG. 1.In addition, control FET 220 having drain 222, source 224, and gate 226,and sync FET 230 having drain 232, source 234, and gate 236, correspondin general to control switch 120 having drain 122, source 124, and gate126, and sync switch 130 having drain 132, source 134, and gate 136,respectively, in FIG. 1. Moreover, switch node contact 229, in FIG. 2,corresponds to switch node 129, in FIG. 1.

The features of semiconductor package 202 will be described in greaterdetail by reference to FIG. 3, and FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4G, and4H (hereinafter “FIGS. 4A-4H”). However, it is noted in reference toFIG. 2 that the electrical connection between source 224 of control FET220 and drain 232 of sync PET 230 is established in the absence of aconductive clip or other feature implemented solely or primarily as anelectrical connector. Instead, according to the implementation shown inFIG. 2, the electrical connection between source 224 and drain 232establishing switch node contact 229 is advantageously provided by syncconductive carrier 210 b and conductive buildup layer or layers 221 c.As a result, the packaging solution of FIG. 2 provides a robust, lowresistance, and low parasitic connection for providing switch nodecontact 229. Moreover, the inventive concepts disclosed by the packagingsolution represented in FIG. 2 can be extended to enable the fabricationof high density MCM packages, with reduced parasitics and improvedthermal performance.

Referring to FIG. 3, FIG. 3 shows flowchart 300 presenting an exemplarymethod for fabricating a semiconductor package suitable for use as apower converter package and including a vertically stacked driver IC. Itis noted that the method described by flowchart 300 is performed on aportion of a conductive carrier structure, which may be a semiconductorpackage lead frame, or may take the form of a conductive sheet or plate,for example.

With respect to FIGS. 4A-4H, structures 410 through 417 shownrespectively in those figures illustrate the result of performing themethod of flowchart 300. For example, FIG. 4A represents contiguousconductive carrier 410 before processing (310), structure 411 showscontiguous conductive carrier 410 after attachment by a control FET anda sync FET (311), structure 412 shows structure 411 after the formationand patterning of a dielectric layer (312), and so forth. It is notedthat contiguous conductive carrier 410, in FIGS. 4A through 4F,corresponds in general to, and serves as a foundational structure for,control conductive carrier 210 c, sync conductive carrier 210 b, andconductive carrier section 210 a, in FIG. 2. It is further noted thatalthough FIGS. 4A-4H depict formation of structures including twodielectric layers and two conductive buildup layers, otherimplementations using the present concepts may include more, or less,than two dielectric layers and two conductive buildup layers.

Referring to flowchart 300, in FIG. 3, in combination with FIG. 4A,flowchart 300 begins with providing contiguous conductive carrier 410having die side 408 and opposite I/O side 418 (310). As shown in FIG.4A, contiguous conductive carrier 410 is represented as an unpatternedconductive sheet or plate. Contiguous conductive carrier 410 may beformed of any conductive material having a suitably low electricalresistance. Examples of materials from which contiguous conductivecarrier 410 may be formed include copper (Cu), aluminum (Al), or aconductive alloy. In one implementation, contiguous conductive carrier410 may be implemented using a semiconductor package lead frame. It isnoted that die side 408 of contiguous conductive carrier 410 correspondsin general to die sides 208 c and 208 b of respective control and syncconductive carriers 210 c and 2100, in FIG. 2. It is further noted thatI/O side 418 of contiguous conductive carrier 410 corresponds in generalto I/O sides 218 c and 218 b of respective control and sync conductivecarriers 210 c and 210 b, in FIG. 2.

Although not shown in the present figures, in some implementations,contiguous conductive carrier 410 may include a barrier metal layerformed on one or both of die side 408 and I/O side 418. Such a barriermetal layer may be formed of nickel-gold (NiAu) or nickel-palladium-gold(NiPdAu), for example. In some implementations, such a barrier metallayer may serve as an etching mask during patterning or pre-patterningof contiguous conductive carrier 410. Thereafter, such a barrier metallayer can provide a solderable surface at one or both of die side 408and I/O side 418 of contiguous conductive carrier 410.

Moving to structure 411 in FIG. 4B with ongoing reference to FIG. 3,flowchart 300 continues with attaching control FET 420 (Q₁) and sync FET430 (Q₂) to die side 408 of contiguous conductive carrier 410 (311).Control FET 420 includes drain 422, source 424, and gate 426, while syncFET 430 includes drain 432, source 434, and gate 436. As shown in FIG.4B, control FET 420 and sync FET 430 are attached to die side 408 ofcontiguous conductive carrier 410 by electrically conductive die attachmaterial 419.

Electrically conductive die attach material 419 may be any suitablesubstance, such as a conductive epoxy, solder, a conductive sinteredmaterial, or diffusion bonded material formed to a thickness of fromapproximately 0.5 mm to approximately 2.0 mm, for example. Control FET420 and sync FET 430 are shown as power FETs having a vertical topology.That is to say, source 424 and gate 426 are situated on the same side ofcontrol FET 420, while drain 422 is situated on an opposite side ofcontrol FET 420. Similarly, source 434 and gate 436 are situated on thesame side of sync FET 430, while drain 432 is situated on an oppositeside of sync FET 430.

In one implementation, respective control and sync FETs 420 and 430 maytake the form of group IV material based vertical FETs, such as siliconvertical MOSFETs for example. However, in other implementations,respective control and sync FETs 420 and 430 may take the form of groupIII-V based power FETs, such as GaN or other III-Nitride based FETs.Control FET 420, sync FET 430, and electrically conductive die attachmaterial 419 correspond respectively to control FET 220, sync FET 230,and electrically conductive die attach material 219, in FIG. 2. In otherwords, control PET 220 and sync FET 230 correspond respectively tocontrol switch 120 and sync switch 130, in FIG. 1, and may be used toimplement power converter switching stage 101 in that figure.

As shown by structure 412 in FIG. 4C, flowchart 300 continues withforming a dielectric layer over contiguous conductive carrier 410,control FET 420, and sync FET 430, followed by patterning of thedielectric layer to form first patterned dielectric 440 (312). Firstpatterned dielectric 440 may be formed by initially laminating apre-formed dielectric layer onto contiguous conductive carrier 410,control FET 420, and sync FET 430, and then patterning the pre-formeddielectric layer to produce windows 442. Such a pre-formed dielectriclayer may be cut or otherwise patterned from a pre-formable dielectricmaterial, such as an epoxy-phenolic or cyanate ester-epoxy build-upmaterial, for example, or any other pre-formable dielectric utilized inlaminate substrate technology. In one implementation, for example, firstpatterned dielectric 440 may be formed of a B-stage polymeric materialcured during lamination.

Patterning of the dielectric layer to form first patterned dielectric440 including windows 442 can be performed using any known technique,such as etching. First patterned dielectric 442 includes windows 442exposing die side 408 of contiguous conductive carrier 410 adjacent eachof control FET 420 and sync FET 430, as well as exposing sources 424 and434 and gates 426 and 436 of respective control and sync FETs 420 and430. First patterned dielectric 440 corresponds to first patterneddielectric 240, in FIG. 2.

Moving to structure 413 in FIG. 4D, flowchart 300 continues with buildupof a first conductive layer over first patterned dielectric 440, andpatterning of the first conductive layer to form conductive builduplayers 421 a, 421 b, 421 c, and 421 d (hereinafter “conductive builduplayers 421 a-421 d”) (313). Conductive buildup layers 421 a-421 d may beformed of Cu or Al, for example, or may be a metal alloy, such as ametal alloy including Cu and Ni, for example. Conductive buildup layers421 a-421 d may be built up using any suitable technique, such aselectrochemical deposition or an electrolytic plating process, forexample. Conductive buildup layers 421 a-421 d correspond respectivelyto conductive buildup layers 221 a-221 d, in FIG. 2.

Continuing to structure 414 in FIG. 4E, flowchart 300 continues withformation and patterning of a second dielectric layer over conductivebuildup layers 421 a-421 d and first patterned dielectric 440 to producesecond patterned dielectric 450 (314). Like first patterned dielectric440, second patterned dielectric 450 may be formed by initiallylaminating a pre-formed dielectric layer, and then patterning thepre-formed dielectric layer to produce windows 454. As noted above, sucha pre-formed dielectric layer may be cut or otherwise patterned from anypre-formable dielectric material utilized in laminate substratetechnology. In one implementation, second patterned dielectric 450 maybe formed of a B-stage polymeric material cured during lamination.

Patterning of the second dielectric layer to form second patterneddielectric 450 including windows 454 can be performed using any knowntechnique, such as etching. Second patterned dielectric 450 providessurface 452 and corresponds to second patterned dielectric 250 providingsurface 252, in FIG. 2.

Moving to structure 415 in FIG. 4F, flowchart 300 continues with buildupof a second conductive layer over second patterned dielectric 450, andpatterning of the second conductive layer to form respective control andsync gate contacts 427 and 437 (315). The second conductive layer may beformed of Cu or Al, for example, or may be a metal alloy, such as ametal alloy including Cu and Ni, for example. The second conductivelayer may be built up using any suitable technique, such aselectrochemical deposition or an electrolytic plating process, forexample. After buildup, the second conductive layer is patterned to formcontrol gate contact 427 over conductive buildup layer 421 d, and syncgate contact 437 over conductive buildup layer 421 b. Respective controland sync gate contacts 427 and 437 correspond respectively to respectivecontrol and sync gate contacts 227 and 237, in FIG. 2.

Moving to structure 416 in FIG. 4G, flowchart 300 continues withformation of control conductive carrier 410 c and sync conductivecarrier 410 b from contiguous conductive carrier 410 (316). As shown inFIG. 4G, control conductive carrier 410 c and sync conductive carrier410 b may be produced by formation of isolation trenches 460 a, 460 b,and 460 c (hereinafter “isolation trenches 460 a-460 c”) throughcontiguous conductive carrier 410. As further shown in FIG. 4G,isolation trenches 460 a-460 c may be formed at I/O side 418 ofcontiguous conductive carrier 410 and extend from I/O side 418 to firstpatterned dielectric 440.

Isolation trenches 460 a-460 c may be formed using any suitabletechnique, such as etching, or laser ablation, for example, as known inthe art. Formation of isolation trenches 460 a-460 c results information of control conductive carrier 410 c, sync conductive carrier410 b, and conductive carrier section 410 a from contiguous conductivecarrier 410. Thus, in implementations in which contiguous conductivecarrier 410 is a semiconductor package lead frame, control conductivecarrier 410 c, sync conductive carrier 410 b, and conductive carriersection 410 a, may each include a portion of such a lead frame.Isolation trenches 460 a-460 c, control conductive carrier 410 c, syncconductive carrier 410 b, and conductive carrier section 410 acorrespond respectively to isolation trenches 260 a-260 c controlconductive carrier 210 c, sync conductive carrier 210 b, and conductivecarrier section 210 a, in FIG. 2.

It is noted that sync conductive carrier 410 b including conductivebuildup layer 421 c electrically connects source 424 of control FET 420to drain 432 of sync FET 430. In addition, according to the presentexemplary implementation, sync conductive carrier 420 b provides switchnode contact 429. It is further noted, however, that the method offlowchart 300 can be readily adapted such that in other implementationscontrol conductive carrier 420 c may be used to provide switch nodecontact 429.

Although in some implementations, isolation trenches 460 a-460 c mayprovide sufficient electrical isolation to the features of structure 416without a dielectric fill, the method of flowchart 300 may optionallycontinue with filling one or more of isolation trenches 460 a-460 c withinsulator 470, as shown in FIG. 40. Insulator 470 may be formed ofsolder resist, for example, and may be deposited or otherwise formed soas to one or more of isolation trenches 460 a-460 c. Insulator 470corresponds to insulator 270 in FIG. 2.

Moving now to structure 417 in FIG. 4H, flowchart 300 continues withsituating driver IC 494 above one or both of control FET 420 and syncFET 430 (317). As shown in FIG. 411, in one implementation, driver IC494 can be mounted face up over control conductive carrier 410 c andsync conductive carrier 410 b by being affixed to second patterneddielectric 450 at surface 452. Driver IC 494 can be affixed to surface452 using die attach material 493, which may be a conductive or anonconductive die attach material. Driver IC 494 and die attach material493 correspond respectively to driver IC 294 and die attach material293, in FIG. 2.

Structure 417 may undergo additional processing including attachment ofbondwires corresponding to bondwires 296, in FIG. 2, for connectingdriver IC 494 to control and sync FETS 420 and 430. In addition, anencapsulant corresponding to encapsulation material 298, in FIG. 2, maybe applied so as to protect driver IC 494 and/or the bondwireconnections between driver IC 494 and respective control and sync gatecontacts 427 and 437. Thus, the implementations shown and described byreference to FIGS. 2,3, and 4A-4H result in an MCM, such as MCM 202, inFIG. 2, configured to integrate switching stage 101 and driver IC 194 ofFIG. 1 in a single semiconductor package by vertically stacking driverIC 194 over switching stage 101.

Referring now to FIG. 5, FIG. 5 shows a cross-sectional view ofexemplary semiconductor package 502 including vertically stacked driverIC 594, according to another implementation. As shown in FIG. 5,semiconductor package 502 is attached to mounting surface 590, such as aPCB for example, by solder bodies 592. Semiconductor package 502includes control conductive carrier 510 c having die side 508 c andopposite I/O side 518 c connecting semiconductor package 502 to mountingsurface 590. Semiconductor package 502 also includes sync conductivecarrier 510 b having die side 508 b and opposite I/O side 518 b alsoconnecting semiconductor package 502 to mounting surface 590.

Semiconductor package 502 further includes control FET 520 (Q₁) havingdrain 522, source 524, and gate 526, as well as sync FET 530 (Q₂) havingdrain 532, source 534, and gate 536. As shown in FIG. 2, control FET 520is attached to die side 508 c of control conductive carrier 510 c, andsync FET 530 is attached to die side 508 b of sync conductive carrier510 b. Semiconductor package 502 also includes conductive carriersection 510 a, and conductive buildup layers 521 a, 521 b, 521 c, and521 d (hereinafter “conductive buildup layers 521 a-521 d”). Inaddition, semiconductor package 502 includes electrically conductive dieattach material 519, first patterned dielectric 540, insulator 570filling isolation trenches 560 a, 560 b, and 560 c (hereinafter“isolation trenches 560 a-560 c”), and second patterned dielectric 550providing surface 552. Also included as part of semiconductor package502 are control drain contact 523 provided by control conductive carrier510 c, sync source contact 535 provided by conductive carrier section510 a, respective control and sync gate contacts 527 and 537 includingrespective conductive buildup layers 521 d and 521 b, and switch nodecontact 529 provided by sync conductive carrier 510.

Control conductive carrier 510 c, control FET 520, sync conductivecarrier 510 b, sync FET 530, conductive carrier section 510 a, andelectrically conductive die attach material 519 correspond respectivelyto control conductive carrier 210 c, control FET 220, sync conductivecarrier 210 b, sync FET 230, conductive carrier section 210 a, andelectrically conductive die attach material 219, in FIG. 2. In addition,first patterned dielectric 540, isolation trenches 560 a-560 c,insulator 570, contacts 523, 529, and 535, and second patterneddielectric 550, in FIG. 5, correspond respectively to first patterneddielectric 240, isolation trenches 260 a-260 c, insulator 270, contacts223, 229, and 235, and second patterned dielectric 250, in FIG. 2.Moreover, conductive buildup layers 521 a-521 d, and respective controland sync gate contacts 527 and 537, in FIG. 5, correspond respectivelyto conductive buildup layers 221 a-221 d, and respective control andsync gate contacts 227 and 237, in FIG. 2.

In contrast to the implementation shown in FIG. 2, however, the presentimplementation includes driver IC 594 flip chip mounted above at leastone of conductive buildup layers 521 d and 521 b formed over respectivecontrol conductive carrier 520 c and sync conductive carrier 510 b. Asshown in FIG. 5, driver IC 594 is flip chip mounted using solder bumps597. As further shown in FIG. 5, driver IC 594 is covered byencapsulation material 598, corresponding to encapsulation material 298,in FIG. 2. It is noted that semiconductor package 502 including controlFET 520, sync FET 530, and driver IC 594, in FIG. 5, corresponds ingeneral to MCM 102 including control switch 120, sync switch 130, anddriver IC 194, in FIG. 1.

According to the implementation shown in FIG. 5, sync conductive carrier510 b advantageously provides switch node contact 529 and therebyestablishes the electrical connection between source 524 of control FET520 and drain 532 of sync FET 530. Moreover, in addition to providingsync source contact 535, switch node contact 529, and control draincontact 523, respective conductive carrier section 510 a, syncconductive carrier 510 b, and control conductive carrier 510 c provideintegrated heat spreading for dissipation of heat generated in MCM 502away from control and sync FETs dies 520 and 530 into mounting surface590.

Thus, by configuring a conductive carrier utilized as a structuralsupport for a power switch to include one or more conductive builduplayers enabling vertical stacking of the power switch and its driver IC,the packaging solutions disclosed herein advantageously achieve a highlycompact package design. In addition, use of the conductive carrier toprovide integrated heat spreading concurrently provides thermalprotection for the power switch. Moreover, use of such a conductivecarrier to couple a control switch to a sync switch so as to provide aswitch node of a power converter switching stage enables furtherreductions in package size through omission of a conductive clip or anyother feature implemented solely or primarily as a switch nodeelectrical connector from a semiconductor package.

From the above description it is manifest that various techniques can beused for implementing the concepts described in the present applicationwithout departing from the scope of those concepts. Moreover, while theconcepts have been described with specific reference to certainimplementations, a person of ordinary skill in the art would recognizethat changes can be made in form and detail without departing from thescope of those concepts. As such, the described implementations are tobe considered in all respects as illustrative and not restrictive. Itshould also be understood that the present application is not limited tothe particular implementations described herein, but manyrearrangements, modifications, and substitutions are possible withoutdeparting from the scope of the present disclosure.

1. A semiconductor package comprising: a control conductive carrierhaving a die side and an opposite input/output (I/O) side connectingsaid semiconductor package to a mounting surface; a control FET of apower converter switching stage attached to said die side of saidcontrol conductive carrier; a driver integrated circuit (IC) for drivingsaid control FET, said driver IC situated above said control FET andelectrically coupled to said control FET by at least one conductivebuildup layer formed over said control conductive carrier.
 2. Thesemiconductor package of claim 1, further comprising a sync conductivecarrier having another die side and another opposite input/output (I/O)side connecting said semiconductor package to said mounting surface; async FET of said power converter switching stage attached to saidanother die side of said sync conductive carrier.
 3. The semiconductorpackage of claim 1, wherein said driver IC is electrically coupled tosaid at least one conductive buildup layer formed over said controlconductive carrier by bondwire.
 4. The semiconductor package of claim 1,wherein said driver IC is flip chip mounted above said at least oneconductive buildup layer formed over said control conductive carrier. 5.The semiconductor package of claim 1, wherein said control FET comprisesa silicon FET.
 6. The semiconductor package of claim 1, wherein saidcontrol FET comprises a III-Nitride FET.
 7. The semiconductor package ofclaim 1, wherein said power converter switching stage is implemented aspart of a buck converter.
 8. A semiconductor package comprising: a syncconductive carrier having a die side and an opposite input/output (I/O)side connecting said semiconductor package to a mounting surface; a syncFET of a power converter switching stage attached to said die side ofsaid sync conductive carrier; a driver integrated circuit (IC) fordriving said sync FET, said driver IC situated above said sync FET andelectrically coupled to said sync FET by at least one conductive builduplayer formed over said sync conductive carrier.
 9. The semiconductorpackage of claim 8, further comprising a control conductive carrierhaving another die side and another opposite input/output (I/O) sideconnecting said semiconductor package to said mounting surface; acontrol FET of said power converter switching stage attached to saidanother die side of said control conductive carrier.
 10. Thesemiconductor package of claim 8, wherein said driver IC is electricallycoupled to said at least one conductive buildup layer formed over saidsync conductive carrier by bondwire.
 11. The semiconductor package ofclaim 8, wherein said driver IC is flip chip mounted above said at leastone conductive buildup layer formed over said sync conductive carrier.12. The semiconductor package of claim 8, wherein said sync FETcomprises a silicon FET.
 13. The semiconductor package of claim 8,wherein said sync FET comprises a III-Nitride FET.
 14. The semiconductorpackage of claim 8, wherein said power converter switching stage isimplemented as part of a buck converter.
 15. A method for fabricating asemiconductor package, said method comprising: providing a contiguousconductive carrier having a die side and an opposite input/output (I/O)side; attaching a control FET and a sync FET of a power converterswitching stage to said die side of said contiguous conductive carrier;forming a control conductive carrier attached to said control FET and async conductive carrier attached to said sync FET from said contiguousconductive carrier; situating a driver integrated circuit (IC) fordriving said control FET and said sync FET above at least one of saidcontrol FET and said sync FET; electrically coupling said driver IC tosaid control FET and said sync FET using conductive buildup layersformed over said control conductive carrier and said sync conductivecarrier.
 16. The method claim 15, wherein said driver IC is electricallycoupled to said conductive buildup layers formed over said controlconductive carrier and said sync conductive carrier by bondwire.
 17. Themethod claim 15, wherein said driver IC is flip chip mounted above saidconductive buildup layers formed over said control conductive carrierand said sync conductive carrier.
 18. The method claim 15, wherein saidcontrol FET and said sync FET comprise silicon FETs.
 19. The methodclaim 15, wherein said control FET and said sync FET compriseIII-Nitride FETs.
 20. The method claim 15, wherein said power converterswitching stage is implemented as part of a buck converter.